How We Stole the Atomic Bomb (1967)

Original title: Come rubammo la bomba atomica

Franco, an Italian fisherman, witnesses a U.S. Air Force plane crash in the Mediterranean off Egypt carrying a nuclear weapon, and he is then persued by shady spy, named Ciccio, working for a spy organization led by the sinister Dr. Si (Yes) to find the atom bomb before anyone else does to blackmail the world, which leads to Franco and Ciccio forming an unlikely alliance to get the bomb for themselves.